According to the Look North the Emirates started to taxi before been told it had to return, then the airport representative said airlines had the final decision, it just doesn't add up. Perhaps I'm being naive but if the ash cloud is at 20,000 ft why can't they just climb to 19,000ft level off and fly under it until they are in clear air then climb out? Same for arrivals descend sooner and fly under the cloud, sounds simple enough doesn't it?